Method for making clamped helix assemblies



June 2, 1970. G. CERNIK METHOD FOR MAKING CLAMPED HELIX ASSEMBLIES 2 Sheets-Sheet 1 Filed Dec. 30, 1966 51042 daze/W4;

June 2, 1970 Filed Dec. 30. 1966 G. CERNIK METHOD FOR MAKING CLAMPED HELIX ASSEMBLIES 2 Sheets-Sheet 2 United States Patent 3,514,843 METHOD FOR MAKING CLAMPED HELIX ASSEMBLIES George Cernik, Torrance, Calif., assignor to Hughes Allcraft Company, Culver City, Calif., a corporation of Delaware Filed Dec. 30, 1966, Ser. No. 606,203 Int. Cl. B23q 7/00 US. Cl. 29559 4 Claims ABSTRACT OF THE DISCLOSURE In the disclosedmethod for achieving ideal triangulation of a ring-like clamping member, preferably for clamping longitudinal support rods about a helical slowwave structure, inwardly directed force is applied to the clamping member at three points equally circumferentially spaced along its outer surface and in a manner to move two of these points equal distances directly toward the third point while mintaining the third point stationary.

This invention relates to the fabrication of clamped supporting and encasing assemblies for helical slow-wave structures. In particular, the invention relates to a method and apparatus for triangulating clamping members for such assemblies.

In electron beam tubes of the traveling-wave type, a stream of electrons is caused to interact with a propagating electromagnetic wave in a manner which amplifies the electromagnetic wave energy. In order to achieve the desired interaction, the electromagnetic wave is propagated along a slow-wave structure, such as an electrically conductive helix wound about the path of the electron stream. The slow-wave structure provides a path of propagation for the electromagnetic wave which is considerably longer than the axial length of the structure so that the traveling-wave may be made to effectively propagate at nearly the velocity of the electron stream. Slow-wave structures of the helix type are usually supported within an encasing barrel by means of a plurality of (usually three) equally circumferentially spaced electrically insulating rods disposed between the helix and the barrel.

A method which has been employed to mount a helical slow-wave structure and its support rods within an encasing barrel is described in US. Pat. 2,943,228 to Bernard Kleinman and involves making the 'barrel in the form of a resilient tubular metallic clamp. The crosssection of the clamp is initially circular, with a crosssectional area greater than that of the structure-rod subassembly to be inserted within the clamp, but with a normal diameter which is less than that of a circle circumscribing the structure-rod subassembly. The clamp is first distorted by applying forces to three points equally spaced along the circumference of the clamp to alter its crosssection from circular toward triangular and thereby produce a configuration which more closely conforms to that of the structure-rod subassembly. The structure-rod su-bassembly is then inserted into the distorted clamp with the rods intermediate the points of application of the forces. Upon removal of the distorting forces the clamp restores itself toward its original shape and in so doing compresses the rods and the slow-wave structure into a rigid assembly.

A key portion of the aforedescribed slow-wave structure mounting and encasing technique involves distorting the configuration of the clamping barrel from circular toward triangular, a process termed triangulation. In carrying out a triangulation procedure in accordance with conventional methods, such as disclosed in the aforementioned patent, the clamp to be distorted is placed against 3,514,843 Patented June 2, 1970 two fixed surfaces, such as rods, which contact the circumference of the clamp at points spaced 120 apart along its circumference. A movable third surface, which may also be a rod, is brought into contact with the clamp at a circumferential point spaced 120 from each fixed surface contact point. Force applied to the clamp by the movable surface presses adjacent portions of the clamp inwardly, as do resultant reactive forces on the clamp from the fixed surfaces. Alo, there is a net movement of the clamp along the direction of the applied force from the movable surface. The clamp is thus caused to slide somewhat along the fixed surfaces, the sliding movement being opposed by frictional forces at the moving points of contact between the clamp and the fixed surfaces. As a result of restricted clamp movement due to these frictional forces, the portion of the clamp adjacent the initially applied force becomes distorted more than the portions adjacent the reactive forces, with the result that uniform, or ideal, triangulation of the clamp is not achieved.

Accordingly, it is an object of the present invention to provide a method and apparatus for carrying out ideal triangulation of a ring-like clamping member.

It is a further object of the present invention to provide a method and apparatus for altering the cross-section of a ring-like clamping member of resilient material from circular toward triangular in a manner which minimizes the possibility of permanently distorting the clamping member by exceeding the elastic limit of the resilient material.

It is a still further object of the present invention to provide apparatus for triangulating tubular members which is more versatile than prior art apparatus for this purpose in that members of different diameter may be processed without replacing or critically adjusting apparatus parts.

It is still another object of the present invention to provide a method for making a clamped three-rod support assembly for a helical slow-wave structure which is more uniform and which is held in a stronger, more rigid clamped relationship than similar assemblies made by prior art methods.

In accordance with the foregoing objects, the present invention achieves ideal triangulation of a ring-like clamping member by applying inwardly directed force to the member at three points equally circumferentially spaced along its outer surface and in a manner to move I two of these points equaldistances directly toward the third points while maintaining the third points stationary.

Triangulating apparatus in accordance with the in vention includes a block which defines an elongated groove having a flat bottom surface and first and second side surfaces each disposed at an angle of with respect to the bottom surface, and first and second equilateral triangular prisms movably disposed in the groove. Each of the prisms has a first lateral surface slidably disposed along one of the side surfaces of the groove, a second lateral surface adapted to contact a tubular member to be triangulated which is disposed within the groove in contact with its bottom surface, and a third lateral surface. Means are provided for applying pressure to the third lateral surface of each of the prisms to caus the prisms to move inwardly along the side surfaces toward thebottom surface of the groove and toward one another, thereby deforming the tubular member so as to provide ideal triangulation thereof.

Additional objects, advantages and characteristic features of the present invention will become readily apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings in which:

FIGS. 1 (a) and (b) are perspective views illustrating the fabrication of a clamped helix supporting and encasing assembly by employing a technique including triangulation of the encasing barrel;

FIG. 2 is a schematic view illustrating distortion of an initially circular clamp in accordance with ideal triangulatiom FIG. 3 is a schematic view illustrating distortion of an identical initially circular clamp in accordance with prior art triangulatiom FIG. 4 is a perspective view illustrating apparatus in accordance with the present invention while functioning to carry out a triangulation procedure according to the method of the invention; and

FIG. 5 is a schematic view illustrating triangulation of an initially circular clamp in accordance with the method of the invention.

Referring to the drawings with greater particularity, in FIG. 1(a) there is shown a subassembly consisting of a helical slow-wave structure 11 and three insulating support rods 12, 14 and 16 disposed about the slow-wave structure 11 120 apart along its circumferential surface. The helix 11 may be of a metal such as molybdenum, while the rods 12, 14 and 16 may be of a ceramic material such as beryllia. The helix-rod subassembly 10 is to be inserted into a resilient clamping and enveloping barrel 18, shown in FIG. 1(b), and which barrel may be of molybdenum, for example. The cross-sectional area within the barrel 18 is greater than the cross-sectional area of the subassembly 10. However, the interior diameter of the barrel 18 is less than the diameter of a circle circumscribing the subassembly 10.

As is shown in FIG. 1(b), the configuration of the barrel 18 'is distorted by applying inwardly directed forces 20, 22 and 2.4 to the barrel 18 along three axially extending lines spaced 120 apart along the outer circumferential surface of the barrel 18-. These forces distort the crosssection -of the barrel 18 from circular toward triangular by an amount sufficient to enable the subassembly 10 to fit into the distorted barrel 18, but which amount is within the elastic limit of the barrel material. After insertion of the subassembly 10 into the barrel 18, the distorting forces are removed. By spring-like action the barrel 18 then restores itself toward its original shape and in so doing compresses the rods 12, 14 and 16 against the helix 11 to form a rigid clamped assembly.

In carrying out the aforedescribed helix assembly fabrication technique, the triangulation of the clamping barrel is critical because the barrel must be distorted sufficiently to permit insertion of the subassembly but not distorted so much that its elastic limit is exceeded. In FIG. 2 there is illustrated an initially circular member undergoing uniform, or ideal, triangulation. The member to be distorted initially has a configuration shown by circle having its center at 32. Forces 34, 36 and 38 are applied to the circle 30 in the direction of its center 32 at respective points 44, 46 and 48 which are located 120 apart along the circumference of the circle 30. As a result of these forces, the points 44, 46 and 48 are uniformly moved inwardly to new locations 44', 46 and 48, with respective points 54, 56 and 58 diametrically opposite the points 44, 46 and 48 moving outwardly by a greater amount to new locations 54', 56 and 58', whereby the shape of the circle 30 is altered to the more triangularlike figure 30'. The resultant ideally triangulated figure 30' is one for which a circle 40 can be drawn which is tangent to the figure 30 at its three most inwardly compressed points 44', 46' and 48'; and another circle 50 can be drawn which is tangent to the figure 30' at its three most outwardly extended points 54, 56' and 58'.

In FIG. 3, there is illustrated an initially circular member being triangulated by conventional techniques. The member to be distorted is shown as initially having the configuration of a circle 130 centered at 132. The circle 130 is supported by first and second fixed surfaces 131 and 133 which contact the circle 130 at respective points 146 and 148 located 120 apart along the circumference of the circle 130. A movable third surface 135 is brought into contact with the circle 130 at a point 144 spaced from the points 146 and 148 along the circumference of the circle 130. A force 134 is applied to the circle by moving the surface 135 inwardly toward the center 132. Reactive forces 136 and 138 are generated at the points 146 and 148 by the resultant pressure of the circle 130 against the surfaces 131 and 133.

The forces 134, 136 and 138 not only distort the configuration of the circle 130, but they also cause a net movement of the circle 130 along the direction of the applied force 134. This movement, however, is opposed by frictional forces 137 and 139 generated as the contacting portions of the circle 130 slide against the respective surfaces 131 and 133. It will be apparent that as the circle 130 moves, the forces 136 and 138 are no longer applied to the circle 130 at respective points 146 and 148, but rather these forces are applied to different points along the circumference of the circle 130 as they move into contact with the surfaces 131 and 133. The points 144, 146 and 148 along the circle 130 where the respective forces 134, 136 and 138 were initially applied are eventually moved to new locations 144', 146' and 148', respectively, as the circle 130 is altered to the more triangular-like figure 130.

It may be seen from FIG. 3 that in addition to a movement of each of the points 144, 146 and 148 along the direction of the applied force 134, the point 144 moves inwardly by a much greater amount than the points 146 and 148. Another way of stating this is that the relative outward movement of points 156 and 158 diametrically opposite the respective points 146 and 148 to new locations 156 and 158', respectively, is greater than the relative outward movement of the point 154 diametrically opposite the point 144 to new location 154. The resultant figure 130' may be seen to not be uniformly, or ideally, triangulated because no circle can be drawn which is tangent to the figure 130' at either its three innermost points or its three outermost points. Note also that whereas the lines joining the points of application of the forces at the onset of this triangulation procedure define an equilateral triangle, the triangle becomes nonequilateral as the triangulation proceeds on account of the non-uniform movement of these points.

It should be apparent that, for a given amount of overall triangulation, there is a greater likelihood of exceeding the elastic limit of the resilient material being triangulated when the triangulation is non-uniform than if it could be uniform. Exceeding the elastic limit of a slow-wave structure clamping member could result in permanent distortion of the clamping member after removal of the distorting forces, and thereby achieve weaker, less rigid clamping of the slow-wave structure subassembly.

It is also pointed out that for apparatus employed to carry out a triangulation procedure in accordance with the prior art method illustrated in FIG. 3, when members of different diameters are to be triangulated, the triangulating apparatus must be adjusted so as to position the fixed surfaces 131 and 133 the appropriate distance apart. For prior art apparatus this necessitates either a change of parts or a critical adjustment and rigid securing of movable parts.

Trian gulating apparatus in accordance with the present invention is illustrated in FIG. 4 and may be seen to include a block 70, of hardened tool steel for example, which defines an elongated work-receiving groove 72. The groove 72 has a fiat bottom surface 74 and first and second flat side surfaces 76 and 78, respectively, each of which is disposed at an angle of 120 with respect to the bottom surface 74. A barrel 18 to be triangulated may be disposed in the groove 72 in contact with the bottom surface 74. A first equilateral triangular prism 80, of hardened tool steel for example, is disposed in the groove 72 such that a first of its three lateral surfaces rests against groove side surface 76 and a second of its lateral surfaces rests against the barrel 18. A second equilateral triangular prism 82, identical to the prism 80, is disposed in the groove 72 such that a first of its three lateral surface rests against groove side surface 78 and a second of its lateral surface r'e'sts against the barrel 18. The aforementioned angular construction of the groove 72 and of the prisms 80 and 82 is such that the block 70 and the prisms 80 and 82 will contact the barrel 18 at points spaced 120 apart along the circumference of the barrel for barrels of varying diameter.

A pressure applying block 84, of hardened tool steel for example, is movably disposed above the groove 72, and a spacer block 86, which may also be of hardened tool steel, is disposed between the pressure applying block 84 and the third lateral surface of each of the prisms 80 and 82. Downward force 88 applied to the pressure block 84 along its longitudinal center line is transmitted by the spacer block 86 to the prisms 80 and 82. The prisms 80 and 82 are thus made to slide along the respective groove side surfaces 76 and 78 toward the bottom surface 74 and toward one another, and in so doing, they provide ideal triangulation of the barrel 18.

The manner in which the present invention is able to provide ideal triangulation of ring-like members should become more apparent by making reference to FIG. which illustrates an initially circular member undergoing triangulation in accordance with the invention. This member is shown as initially having the configuration of a circle 230 centered at 232 and having the same diameter as the circles 30 and 130 of FIGS. 2 and 3, respectively. As the block 86 is urged against the prisms 80 and 82, the prisms 80 and 82 apply respective forces 236 and 238 to the circle 230 in directions toward the center 232. A reactive force 234 which is also directed toward the center 232, is generated by the resultant pressure of the circle 230 against the surface 74. The prisms 80 and 82 and the surface 74 contact the circle 230 at respective points 244, 246 and 248 which are located 120 apart along the circumference of the circle 230.

As the block 86 is moved toward the surface 74, the prisms 80 and 82 slide along the respective groove side surfaces 76 and 78 toward the groove bottom surface 74 and toward one another. On account of the angular relationship between the groove surfaces 74, 76 and 78 and the surfaces of the prisms 80 and 82, as the prisms 80' and 82 move, the points of contact 246 and 248 move the same distance directly toward the point of contact 244, and each point 246 and 248 moves toward the other point by half of this distance, producing the same relative movement between each of the points 244, 246 and 248. Thus, the lines joining the points of application of the forces 234, 236 and 238 to the circle 230 always define an equilateral triangle even though the points of application of the forces 236 and 238 undergo movement in absolute space. Hoyever, these points do not move relative to the circumference of the circle 230, but rather they each remain 120 away from the point 244 along the circumference of the circle 230 even though the circle 230 changes its shape.

When the surface of the prisms 80 and 82 which contact the circle 230 have moved to new locations illustrated by dashed lines 90 and 92, respectively, the points 246 and 248 have moved to new locations 246' and 248, respectively, and the circle 230 is altered to the more triangular-like figure 230'. However, since an equilateral triangular relationship is maintained between the points 244, 246246, and 248'248, a circle can be drawn which is tangent to the figure 230' at its three innermost points 244, 246 and 248', and another circle can be drawn which is tangent to the figure 30 at its three outermost points 254', 256 and 258' which lie diametrically opposite to the respective points 244, 246' and 248. Thus, the figure 230' may be seen to be ideally triangulated.

By using the method and apparatus of the present in vention, ideal triangulation of barrels such as 18 can actually be achieved. As a result, the possibility that the elastic limit of the barrel material will be exceeded during distortion is minimized, thereby reducing the tendency for permanent distortion of the barrel 18 after removal of the distorting forces. Moreover. the resultant clampedhelix assemblies made with ideally triangulated barrels are held in a stronger, more rigid clamped relationship than for similarly dimensioned assemblies employing barrels which have not been uniformly triangulated. In addition, it will be apparent that barrels of varying diameter may be triangulated by apparatus according to the present invention without making any change in the apparatus, because the angular relationship of the prism and groove surfaces ensures triangulating" forces will be applied and maintained apart along the barrel surface regardless of barrel size.

Although the present invention has been shown and described with reference to a particular method and apparatus, nevertheless, various changes and modifications obvious to a person skilled in the art to which the invention pertains are deemed to lie within the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A method for distorting the configuration of a ringlike clamping member to alter its cross-section from circular toward triangular comprising: applying inwardly directed force to said member at three points equally circumferentially spaced along the outer surface thereof and in a manner to move two of said points directly toward the third of said points while maintaining said point stationary, said two of said points being moved equal distances.

2. A method for distorting the configuration of a ringlike clamping member to alter its cross-section from circul'ar toward triangular comprising: applying inwardly directed force to said member at three points equally circumferentially spaced along the outer surface thereof, whereby the lines joining respective pairs of said points define an equilateral triangle, and moving two of said points directly toward the third of said points while maintaining said third point stationary such that said lines continue to define an equilateral triangle.

3. A method for distorting the configuration of a tubular clamping member to alter its cross-section from circular toward triangular comprising: applying inwardly directed force to said member alongthree axially extending lines equally circumferentially spaced along the outer surface thereof and in a manner to move two of said lines directly toward the third of said lines while maintaining said third line stationary, said two said lines being moved equal distances.

4. A method for distorting the configuration of a tubular clamping member to alter its cross-section from circular toward triangular comprising: applying inwardly directed force to said member along three axially extending lines equally circumferentially spaced along the outer surface thereof, whereby the plane's joining respective pairs of said lines and a pair of planes perpendicular to said lines define an equilateral triangular prism, and moving two of said lines directly toward the third of said lines while maintaining said third line stationary such that said planes continue to define an equilateral triangular prism.

References Cited UNITED STATES PATENTS 5/1959 Barish 29453 X 3/1881 Morse 72367 U.S. Cl. X.R.

mg? UNITED S'FA'IICS IA'KISN'I OFFICE CERIIFICATE OF CORRECTION Patent No. 3,514,843 D t d June 2, 1970 Inventor(s) G. Cernik It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

531. 2, line 9, "A10" should be -Also-; 1

2, line 48, "points" (both occurrences) should be point-. Col. 5, line 55, "Hogever" should be However-;

5, line 60, "surface" should be surfaces-; 5, line 67, "248'" (first occurrence) should be 248--. Col. 6, line 14, after "insures" insert -that .the;

6, line 30, after "said" (second occurrence) insert -third; 6, line 50, after "two" insert -of.

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